Exterior wall structural member for a heat exchanger in a hot-air heater

ABSTRACT

An outside wall panel for a heat exchanger in an air heater furnace wherein the cross-over port structure from the first stage of a heat exchanger is an elongated rectangular inlet into the second stage of the heat exchanger, which has a number of spaced flanges therein for guiding the flow of the products of combustion more evenly in their passage to the outlet of the second stage, the panel having one or more deformations or corrugations based on an isotherm pattern and raised from a flat surface or may be in the form of a pair of concave-convex deformations joined together by gradual curves to define a dimple, this pair also being based on an isotherm pattern.

United States Patent Randall et al.

[ 51 May9, 1972 [72] Inventors: Newton P. Randall; Brian J. Lewis, both of Fishkill, NY.

[73] Assignee: Texaco Inc., New York, NY.

[22] Filed: June 29, 1970 [21] Appl.NO.: 50,576

[5 6] References Cited UNITED STATES PATENTS 2,470,860 5/1949 Parrish ..126/110 X 1,334,039 3/1920 Lape ..126/116 2,263,098 11/1941 Mueller.... ..126/110 3,151,673 10/1964 Strache ..126/116 X Primary Examiner-Charles J. Myhre Attorney-Thomas H. Whaley and Carl G. Reis [57] ABSTRACT An outside wall panel for a heat exchanger in an air heater furnace wherein the cross-over port structure from the first stage of a heat exchanger is an elongated rectangular inlet into the second stage of the heat exchanger, which has a number of spaced flanges therein for guiding the flow of the products of combustion more evenly in their passage to the outlet of the second stage, the panel having one or more deformations or corrugations based on an isotherm pattern and raised from a flat surface or may be in the form of a pair of concave-convex deformations joined together by gradual curves to define a dimple, this pair also being based on an isotherm pattern.

5 Claims, 7 Drawing Figures EXTERIOR WALL STRUCTURAL MEMBER FOR A HEAT EXCHANGER IN A HOT-AIR HEATER BACKGROUND OF THE INVENTION This invention relates generally to hot-air furnace heaters, and particularly to a novel exterior wall structural member for the heat exchange structure therefor, prior to venting the combustion products to the exterior.

Hot-air furnaces are used widely in modern homes. Conventionally, such furnaces include a burner gun assembly firing into a combustion chamber which is joined to some form of radiating means for heating air and which serves as a flue for the discharge of the products of combustion. The radiating means for heating air and which serves as a flue for the discharge of the products of combustion. The radiating means provides a circuitous flow of the hot products of combustion so that a two-stage heat exchanger is suited ideally for heating the air. The air to be heated is provided to a distribution conduit which is spaced around the combustion chamber and radiating means, and adjacent the latter, forms a plenum or distributing space for the ducts leading the heated air to the desired points of reception. Improvements in hot-air furnace construction generally are directed to an increase in the efficiency of combustion and/or heat transfer for more even heat distribution and to lower the temperature of the discharged products of combustion. In the commonly assigned, copending application for patent for a Heat Exchange Structure for a Hot Air Heater, Ser. No. 42,366, filed June l, 1970, by T. L. Tyson and E. G. Craze, Jr., there is disclosed a more effective heat transfer structure whereby the hot products of combustion are distributed more evenly over the extent of the radiating means or heat exchange surfaces by means of flow dividers therein, which are parallel to the normal gas flow therethrough, so that the complexity of the gas flow therein is minimized. Thus, the pressure loss in the flow passages is not increased materially. Concomitant with the use of the flow dividers is the use of a novel cross-over structure to aid in the distribution of the products of combustion in the radiating means.

SUMMARY OF THE INVENTION The invention in general provides for an exterior wall structural member or outside panel of the second stage of the heat exchange surfaces opposite the cross-over port structure between the primary and secondary stages of the heat exchanger, which panel is provided with corrugations or deformations located over isotherm patterns to relieve thermal stresses resulting from the heating and expansion of the panel in this area.

Accordingly, it is an overall object of this invention to provide for an improved heat exchanger construction.

This and other objects, advantages and features of the invention will become more apparent from the following description taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an exposed side view of the furnace assembly with the heat exchanger shown in full outline;

FIG. 2 is an isometric view, partly in section, showing the novel construction of the outside panel of the heat exchanger opposite the cross-over port structure;

FIG. 3 is an isothermal configuration which occurs on the outside panel of the heat exchanger opposite the cross-over port structure during operation of the furnace;

FIG. 4a is a simplified stress diagram on which the novel structure is based;

FIG. 4b is a cross section of an outside panel wherein an expansion ring has been located in relationship to the isothermal pattern of FIG. 3.

FIG. 5 is a view, partly in section, of the outside panel of the heat exchanger opposite the cross-over port structure, illustrating the use of a plurality of corrugations based on the isothermal pattern encountered; and

FIG. 5a is a cross section of the outside panel of the heat exchanger taken along line 5a5a in FIG. 2, illustrating the novel structure applied as a dimple configuration.

DESCRIPTION OF THE PREFERRED EMBODIMENT With reference to FIG. 1 of the drawings, a hot-air furnace cabinet assembly is disclosed at 1, comprising the air intake section 2 with the air blower assembly 3, and a control assembly at 4 positioned therein. The air distributing conduit 5 leads from the air intake section 2 and surrounds the combustion chamber 6 and the radiating means or heat exchange construction 10, the latter being a two-stage heat exchanger which is joined to the combustion chamber by V-band clamp means 9.

A burner gun assembly 7 fires into the combustion chamber 6 and supports the fuel pump assembly and combustion air blower 8 thereon.

The heat exchanger 10 comprises the first stage 11 having the transition portion 11a where the bottom cylindrical structure, which is connected to the circular combustion chamber 6, is changed to a rectangular structure having a closed top 1 1b; and the second stage of the exchanger is shown at 12.

Referring specifically to FIG. 2, partially in section, the two stages of a heat exchanger are shown disclosing the manner in which the cross-over port structure and the support flanges hold the two stages together. The cross-over port structure at 13 is a substantially rectangular vertical inlet into the second stage for the products of combustion leaving the first stage and is flared outwardly to join the inside wall of the second stage. The outlet from the second stage is disclosed as circular at 14 leading to flue 15 (see FIG. 1). This outlet connection and flanges on the opposite panel joined to the cabinet wall (not shown) support the heat exchanger in the cabinet. An inspection door and control air bleed is at 16, shown more completely in FIG. 1, and clean-out ports are disclosed at 17, the covers therefor having been omitted for clarity.

The directing flanges 18 are generally parallel to the flow of the products of combustion from the inlet 13 to the outlet 14, these flanges being spaced to provide equal or proportional volumes in the second stage as desired and having bent directional portions at 18a adjacent inlet 13 for directing the flow in a controlled manner around the second stage, and are also bent adjacent outlet 14 at 18b. In addition to the flared cross-over port structure at 13, support flanges at 19, one only being shown at the cut-away section, are used to hold the two stages together. Ovoid shaped compensating corrugations or deformations in the exterior wall structural member or panel opposite the cross-over port structure are shown at 200 and 20b (also see FIG. 5a), the former corrugation being convex and having its dimensions such that it surrounds the projected dimensions of the cross-over port structure or inlet 13, as shown in FIG. 2, and the latter corrugation being concave to form a dimple. This configuration allows for expansion as a corrugated diaphragm to compensate for any unequal heat distribution patterns resulting from the flow out of the crossover port structure, and are located based on isothermal patterns which have been found to occur on the out-side panel of the heat exchanger.

FIG. 3 shows the general isothermal temperature distribution such as would occur on the outside panel of the heat exchanger opposite the cross-over port structure, which has been superimposed thereon in schematic form. The long axis of the temperature contours corresponds to the long dimension of the cross-over port structure or opening which conducts the combustion gases from the primary to the secondary stage of the heat exchanger. The temperature profile as indicated is in the range of 865 F at the center of the opening down to 650 F on the outer profile, with the lower part of the opening indicating the steepest gradient of isotherms.

FIG. 4a illustrates the stresses which occur along the edges of a corrugation X extending from adjoining lateral surfaces Y. When the expansion rings or compensating corrugations are formed to follow a pattern of isotherms which exists on a particular panel during steady state operation, the thermal stresses which act perpendicular to the isotherms, as denoted by F apply a uniform loading to the cross section and provide the maximum deflection per unit stress to compensate for the thermal expansion.

If the corrugations were to conform to some geometric shape other than that of an isothermal pattern, the stresses would act at some angle other than 90 to the axis of the corrugation, as denoted by F,, in FIG, 4a, and result in less compensating deflection per unit stress, thus allowing higher stresses to exist, ultimately leading to failure of sorts.

F K). 4b illustrates in cross section, a single corrugation 20 formed to compensate for uneven heating such as might be centered on the isotherm shown by the dashed line in HQ. 3. This corrugation could project from a flat surface, or could have the dimpled structure at 2011 and 20b, FlG. 5a, the corru gation 2011 being centered on the dashed line isotherrn of FIG. 3.

FIG. 5 not only discloses the interior spacing or inside passage 21 between the first and second stages of the heat exchanger, but also a series of corrugations 20, which have been centered on a pattern of isotherms, The proportions of this spacing between these stages and that between the exchanger and the cabinet wherein the pumped air is exposed to the heat of the combustion gases in the furnace can be determined by experiment, and likewise the extent of the surface areas of the heat exchanger, the passages and surfaces being chosen in accordance with heating requirements Likewise, the number of corrugations based on the isotherms can be determined.

The deformations are shaped so that the expanding metal moves outward through sections that have very gradual radii thereby reducing stress concentrations such as arise when stiffening corrugations of small radii are employed on this structural member. In addition, the shape tends to grow both in and out, lessening the total growth in either direction. When the center is concave, as shown in FIG. 5a, the flow path of the combustion products is improved aerodynamically, even though the ends of the flanges at 180 adjacent inlet 13 are spaced from the deformation a.

Thus, there has been shown and described how an improved expansion panel for a heat exchange structure can be used in a heater which more evenly distributes hot products of combustion to provide for better heating of air and a lowering of flue gas temperatures.

Other modifications and variations of the invention as hereinbefore set forth may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claims.

lclaim:

1. In the combination defining a heater construction for providing heated air and including combustion means, a heat exchanger structure comprising wall members defining a pair of concentrically spaced, interconnected heat exchange chambers, the first or inner of said chambers being connected to the combustion chamber of said combustion means'and receiving hot products of combustion directly therefrom, the second or outer of said chambers being joined to the first heat exchange chamber by a cross-over port structure defining an inlet thereinto for receiving said products of combustion from said inner of said chambers, and an outlet located in the exterior wall of said outer of said chambers opposite the exterior wall thereof adjacent said inlet for the discharge of said products of combustion from the second heat exchange chamber, the improvement comprising the exterior wall of said second heat exchange chamber adjacent said cross-over port structure having a corrugated configuration to counteract heat transfer thereto, the location; number and size of the deformation of said configuration being in relation to thermal gradients on said exterior wall and being appropriately shaped to reduce stresses from thermal ex ansion.

2. In the combination as define in claim 1, said cross-over port structure being substantially rectangular in configuration and extending vertically at the junction between said chambers whereby the flow of said products of combustion into said second heat exchange chamber is more widely distributed adjacent said inlet and itself provides additional heat exchange surface, said second chamber having a plurality of flow divider flange strips extending from adjacent said outlet for controlled guidance of the flow of said products of combustion therebetween, said flange strips being substantially parallel to the normal flow of said products of combustion in said second chamber to minimize the complexity of said flow therein and to keep the pressure loss at a minimum.

3. In the combination as defined in claim 2, the spacing between said chambers of said heat exchanger structure and the surface areas of said chambers being determined by the air heating requirements.

4. In the combination as defined in claim 3, said deformation of said configuration following an isotherm on said exterior wall said deformation being convex and being joined to the rest of the exterior wall structural member by gradual curves.

5. in the combination as defined in claim 4, the convex deformation being one of a pair of deformations, the other of said pair being concave to define a dimple, the dimensions of said configuration being such as to surround said cross-over port structure. 

1. In the combination defining a heater construction for providing heated air and including combustion means, a heat exchanger structure comprising wall members defining a pair of concentrically spaced, interconnected heat exchange chambers, the first or inner of said chambers being connected to the combustion chamber of said combustion means and receiving hot products of combustion directly therefrom, the second or outer of said chambers being joined to the first heat exchange chamber by a cross-over port structure defining an inlet thereinto for receiving said products of combustion from said inner of said chambers, and an outlet located in the exterior wall of said outer of said chambers opposite the exterior wall thereof adjacent said inlet for the discharge of said products of combustion from the second heat exchange chamber, the improvement comprising the exterior wall of said second heat exchange chamber adjacent said cross-over port structure having a corrugated configuration to counteract heat transfer thereto, the location, number and size of the deformation of said configuration being in relation to thermal gradients on said exterior wall and being appropriately shaped to reduce stresses from thermal expansion.
 2. In the combination as defined in claim 1, said cross-over port structure being substantially rectangular in configuration and extending vertically at the junction between said chambers whereby the flow of said products of combustion into said second heat exchange chamber is more widely distributed adjacent said inlet and itself provides additional heat exchange surface, said second chamber having a plurality of flow divider flange strips extending from adjacent said outlet for controlled guidance of the flow of said products of combustion therebetween, said flange strips being substantially parallel to the normal flow of said products of combustion in said second chamber to minimize the complexity of said flow therein and to keep the pressure loss at a minimum.
 3. In the combination as defined in claim 2, the spacing between said chambers of said heat exchanger structure and the surface areas of said chambers being determined by the air heating requirements.
 4. In the combination as defined in claim 3, said deformation of said configuration following an isotherm on said exterior wall said deformation being convex and being joined to the rest of the exterior wall structural member by gradual curves.
 5. In the combination as defined in claim 4, the convex deformation being one of a pair of deformations, the other of said pair being concave to define a dimple, the dimensions of said configuration being such as to surround said cross-over port structure. 